Patent GB-967070-A (GB)
Title: Improvements in or relating to testing apparatus for information storage devices
Inventor: JAMES JOHN BERNARD
IPC: G11C29/56
Filed: 1960-12-30
Abstract: 967,070. Electric tests. INTERNATIONAL COMPUTERS & TABULATORS Ltd. Nov. 7, 1961 [Dec. 30, 1960], No. 44763/60. Heading G1N. [Also in Division H3] Testing of discrete storage regions of an anisotropic thin magnetic film deposited on a supporting substrate is effected by pressing the film against a test matrix of conductors and sequentially applying test signals to the conductors. The test matrix of conductors is located in the same relative position with respect to the film as the conductors of a storage matrix in which the film under test is ultimately to be incorporated. The testing apparatus comprises a base plate 1, Figs. 1 and 3, carrying a film support block 2 having recesses 3 for insulated row, column and pick-up conductors 4, 21, 12. The magnetic film with the substrate 18 uppermost is positioned by locating strips 20, 31 on to the film support block, and is pressed into close contact by a weight 32. The test matrix wiring is terminated at contacts 10, 13 and 28 in terminal blocks 11, 29 and 14 (not shown), the column and pick-up conductors having common return paths by way of spring contacts through the weight and either through the substrate, if conductive, or a conductive layer insulated from the weight, Fig. 2 (not shown). The test circuit is shown in Fig. 4 in which depression of a start key 63 opens an AND gate 61 through a start-stop trigger pair 62 and applies impulses from a generator 60 to a stepping register 36. Each complete cycle of register 36 steps register 49 by one stage, and this register in turn steps register 53 till the registers are of the recirculating type. Thus only a single one of each of the AND gates 52, 55, 56 are opened at any time, so that operative connections are made for only a single row and a single column conductor 4, 21, and only the associated pick-up conductor 12 is effectively connected to an output register 59. The row and column conductors are coincidently energized by drives 46 and 47 or 48 as register 36 is stepped, the pattern of energizations being determined by the connections of a cross-connection field 41 between the register and trigger pairs 43, 44, 45. Switching of the discrete film area located at the intersection of the operative row and column conductors 4, 12 depends on the direction of current in each conductor, the drives 47, 48 providing respective pulses of opposite polarity while drive 46 overcomes a steady bias acting in the opposite direction. With the cross field connected as shown, the pattern of energizations at each discrete film area in turn comprises the test pattern 00110. For the zero digit registration drives 46 and 47 are both operative, both triggers 43, 44 being set to the output state by signals over the cross field. The pulses are terminated when the register 36 steps to the next stage and resets the triggers. For a binary one registration only the drive 47 is energized by setting trigger 44 to the output state, this operation being terminated by resetting the trigger. To read out, the reverse drive 48 is energized by setting trigger 45 and subsequently resetting. The test pattern used comprises the steps of storing and then reading zero, storing zero followed by storing one without intermediate read-out, reading out one, storing one followed by storing zero without intermediate read-out, followed by read-out of the stored zero. On the completion of the cycle register 49 steps one stage and opens the AND gate 52 of the next column 21. When test of all the film areas in a row is completed, register 53 steps and opens AND gates 55, 56 in the next row. When all the film areas have been tested, outputs from the final stages of registers 36, 49, 53 open on AND gate 64 and reset the start trigger 62 after delay in 65. Start and terminating signals are sent from trigger 62 to the output register which indicates whether the test cycles are satisfactory. Specification 942,561 is referred to.